Deposed Kyrgyz President Askar Akayev has formally resigned, making him only the second Central Asian leader to leave power since the region became independent from the Soviet Union 14 years ago.

His sudden overthrow by massive popular protests in late March left Kyrgyzstan briefly without a government, but the anti-Akayev opposition soon took over.

The transition of power has been largely peaceful, and the opposition's main leader, Kurmanbek Bakiev, has been appointed as interim president.

But there are concerns about the stability of the new government.

A rift in the leadership emerged almost immediately after Mr Akayev's departure. While Mr Bakiev was leading the protests, another main opposition leader, Felix Kulov, was languishing in prison.

He was convicted of corruption and jailed four years ago, on charges which were widely seen to be politically motivated.

Mr Kulov was freed from prison during the protests, and within days, signs began to emerge of disagreements between him and Mr Bakiev.

There are signs that Felix Kulov and Kurmanbek Bakiev disagree

Mr Kulov has already resigned the position of head of security, given to him in the days after Mr Akayev was ousted, and he is thought to be preparing to stand as a candidate in the presidential elections which have already been announced for 26 June.

He has wide popular support, but there are legal obstacles to clear before he can run for president.

"Kulov has to lose the criminal charges against him," said David Lewis, Central Asia project director of Crisis Group, a Brussels-based international think-tank.

"And they'll have to do away with the language requirement because he doesn't speak Kyrgyz."

By law, the president must speak Kyrgyz fluently. But Mr Kulov, like many people from northern Kyrgyzstan, speaks better Russian.

Geographical division

Officials from the Organisation for Security and Co-operation in Europe (OSCE) have been meeting the new leadership to try to ensure a smooth transition of power.

Dimitrij Rupel, the organisation's current chairman, said the competition between the two men was worrying.

"It's something which should concern us all," he said. If Mr Kulov is excluded from the upcoming presidential race for legal reasons, it is feared there could be a backlash and possible further protests.

The Bishkek newspaper MSN, a mouthpiece for the former opposition, went so far as to warn of possible civil war if tensions continued to grow within the new leadership.

That possibility remains remote, but it reflects a real concern in Kyrgyzstan.

The divisions between these two politicians reflect a geographical division that will present a challenge for the new government.

Mr Kulov is from the Bishkek region of northern Kyrgyzstan, while Mr Bakiev is from Jalal-Abad, in the south.

Political power - and much of the country's new wealth - is concentrated in the north, especially in the capital.

The south, around the Fergana valley, is poorer and has often felt its concerns are overlooked in Bishkek.

Significantly, the protest movement which overthrew Mr Akayev began in the south, and only spread to Bishkek in the final days before he fled.

Muratbek Imanaliyev, a former Kyrgyz foreign minister, says it is essential that both north and south feel they have a stake in the new government.

He suggests that a small advisory group of international experts should be established before the upcoming elections, to examine the relationship between Bishkek and the regions and also the question of Kyrgyzstan's pressing economic problems.

Economic problems

The lack of economic improvement is the fundamental cause of the anger which led to the protest movement.

Any new government must address the issue in order to win popular backing.

Kyrgyzstan's mountains split the north and south

Kyrgyzstan is mostly mountainous, with few natural resources. It is cursed with Soviet-era borders which cut off many of its trading towns from their natural economic hinterland.

Mr Imanaliyev, however, thinks these obstacles can be overcome.

"The economic problems won't be solved immediately," he said, "but with a strong president and strong government, you can bring improvements. The first problem is to reduce corruption, and then we need a professional government with capable people at all levels."

Kyrgyzstan is bound to look to the international community for support in this transition period.

While Russia is a historical ally, the United States will also figure prominently in the country's international relations. Both have military bases in Kyrgyzstan.

President Akayev accused American organisations of being behind his country's "velvet revolution".

US-funded organisations have certainly been working in Kyrgyzstan to promote greater democracy, as in all ex-Soviet countries. But Felix Kulov and others in the new leadership have denied any suggestion of US involvement.

Washington's main interest in Kyrgyzstan, and the rest of Central Asia, is for stable local governments which can prevent the spread of Islamic extremism and the growth of heroin smuggling from nearby Afghanistan.

These are concerns shared by Europe and Kyrgyzstan's big eastern neighbour, China, as well.